What is bone cancer?

Causes and Symptoms

Out of about one million new cancers that are diagnosed annually in the United States, less than 0.2 percent are primary bone cancer. The American Cancer Society estimates that approximately 3,010 new cases of bone cancer will be diagnosed in 2013. Most of these cases arise in children under the age of twenty. If diagnosis is made before the bone cancer has spread to the lungs or other sites in the body, prompt treatment by surgery, radiation, or chemotherapy can provide a good prognosis for recovery.

In older adults, most cases of so-called bone cancer actually are secondary tumors that have spread from other parts of the body, especially from the breast, prostate, thyroid, lung, or kidney. Such metastasized tumors consist of cells that are characteristic of their original, primary site. Secondary bone cancers are far more common than those which start in the bone.

The first symptom of bone cancer in children usually is a localized swelling followed by persistent, dull pain. It is easily mistaken for a sprain or a bruise that might come from a minor injury. Additional symptoms are fatigue, fever, loss of appetite, and other signs of general illness. Unfortunately, early symptoms may be ignored until the disease has already spread to other parts of the body. Before chemotherapy became available in the 1970s, the spread of bone cancer to the lungs occurred within two years for about 80 percent of patients.

A variety of diagnostic techniques are available to the physician if the examination of a patient arouses the suspicion of bone cancer. Blood tests, including a study of liver and kidney functions, have become increasingly useful because of improvements in analytical procedure. X-ray photography and computed tomography (CT) scanning will give pictorial evidence of any lesions or excess bony growth. Magnetic resonance imaging (MRI) provides the best visualization of tumors extending into soft tissue. Finally, the most important diagnostic procedure is
biopsy. Usually, the bone is opened surgically and a sample of tissue is taken. Sometimes, a hollow needle inserted through the bone cortex can be used to withdraw a small sample. A pathologist who specializes in oncology examines the tissue under a microscope to confirm if cancer cells are present and to identify their type.

Magnetic resonance imaging as a diagnostic technique was developed in the 1980s, giving remarkable picture clarity for soft tissue. A strong magnetic field and radio waves are used to determine the concentration of hydrogen in a region of the body. Since tissue is mostly water (which contains hydrogen) and bone is dry, the image will show bright areas for tissue or soft organs against a dark background. Also, MRI shows contrast between normal tissue and a denser, tumorous mass.

Another diagnostic technique, the bone scan, is used to investigate whether a tumor has metastasized to other bones in the body. A small amount of radioactive tracer, usually technetium, is injected into the patient. It circulates in the bloodstream and gradually accumulates in the
bone marrow. After several hours, radiation counters are used to scan the entire skeleton from head to foot. Regions of rapid cell growth, which may signal a tumorous mass, are indicated by a relatively high counting rate. If secondary tumors are detected by the bone scan, their shape and size can be investigated further using MRI.

Several kinds of bone cancer have been identified. One type is called osteosarcoma. It occurs most frequently during puberty, when a child’s bones are growing rapidly. The tumor is likely to develop inside the long bones of the arms, in the legs near the knee, or in the pelvis. As its size increases and the surrounding bone material becomes soft, the bone may fracture because of internal pressure in the bone. Osteosarcomas also may grow on the exterior surface of bones, producing hard spikes that radiate outward. Another type of bone cancer is called Ewing’s sarcoma. MRI and CT scans commonly exhibit a “moth-eaten” appearance where bone destruction has taken place. Both the inner (medullary) cavity and the outer cortex of the bone can be affected. Subsequently, a tumorous mass develops within the covering of tissue that surrounds the bone. This abnormal growth tends to form concentric layers, like the skin of an onion. The localized swelling expands in size, causing soreness and eventually impeding motion at the joints.

Bone cancer can take a variety of other forms. For example, a tumor may invade the bone from the outside and then penetrate into the medullary cavity. To make an accurate diagnosis and institute the best possible treatment for bone cancer, particularly for children, it is important for patients and their families to find an oncologist and supporting staff with specialized experience in this relatively rare condition. In general, the orthopedic surgeon who does the biopsy should be a specialist who is trained to do the ultimate bone surgery, so that any cancer cell contamination at the site of the biopsy will be completely removed.

Treatment and Therapy

To develop an appropriate treatment plan for a patient with bone cancer, all the relevant diagnostic information must be brought together. A medical team consisting of a radiologist, pathologist, radiation therapist, orthopedic surgeon, and medical oncologist will assess how far the cancer has advanced. This is called staging, that is, classifying its stage of growth.

Three designations commonly are used to characterize a cancer: G for its grade (based on the microscopic tissue analysis), T for tumor size and penetration, and M for evidence of metastasis. For example, (G1) (T2) (M0) would describe a low-grade tumor (G1) that has broken out of its bone compartment (T2) but has not metastasized (M0) to the lungs or elsewhere.

Before 1970, treatment of a cancerous bone normally meant
amputation. The prognosis for recovery was less than 20 percent, however, because microscopic, invisible metastases to the lungs and other organs usually were already present. The experimental search for drugs that can fight cancer cells started in the 1930s. Charles B. Huggins discovered that the female sex hormone estrogen could halt the growth of prostate cancer in men. He received the Nobel Prize in Medicine in 1966 for his work. Since that pioneering success, several hundred thousand drugs have been tested, with less than a hundred showing any substantial benefit. The anticancer drugs also can have severe side effects on healthy cells. Fortunately, a rapidly growing tumor has a higher rate of metabolism, so drugs will kill the cancer cells at a lower dose and spare most normal cells.

An effective method of treating bone cancer in children is to use chemotherapy or radiation even before surgery, in order to shrink the size of a tumor. Instead of complete amputation, the surgeon may need to remove only part of a bone, thus saving the limb. Even when a bone joint must be amputated, it may still be possible to salvage the limb by inserting an artificial joint or one from an organ donor.

In older adults, cancer of the bone almost invariably is caused by metastasis from another location in the body. The tumor in the bone may be very painful. Radiation to the affected area can provide palliative treatment, while more aggressive action is taken against the primary cancer site.

A wide range of medications is available to help control pain and to counteract the disagreeable side effects of radiation or chemotherapy. Special attention is given to the diet of cancer patients to prevent weight loss and to maintain body strength. Loss of appetite and digestion problems are common symptoms during therapy. Strong painkilling drugs such as codeine and morphine sometimes are necessary. The dose should be limited, however, so that the patient’s ability to interact socially is not completely lost.

Vigorous research to find more effective therapies for cancer is widely supported. The goal is to find procedures that are less mutilating, less expensive, and less painful for the patient. Promising new drugs must be tested to determine how large a dose is needed and how serious the side effects are. Therefore, patients may be asked to become volunteers in a clinical trial of an experimental treatment. Although people have a justified sense of reluctance to become “guinea pigs” in an untested therapy, clinical trials with human subjects have been essential in the development of successful medical procedures. Firm guidelines have been established for testing new therapies, such as the requirement to obtain the informed consent of patients and their families. In addition, doctors in the United States are responsible to a medical oversight committee and are obligated to submit their results for professional review. Cancer treatment can make progress through willing participation by patients in the carefully planned clinical trials.

Perspective and Prospects

Bone cancer first came to the attention of the public in the 1920s through a notorious case of industrial poisoning. A manufacturing company in New Jersey was utilizing radioactive radium to make watch dials that would glow in the dark. The women workers who were hired to apply the luminous paint would twirl the paint brushes between their lips to make a fine tip. The ingested radium, being chemically similar to calcium, became concentrated in bones, especially of the jaw and neck. Eventually, more than forty workers died of bone cancer, including the company’s chief chemist.

After this incident, it became clear that radiation has a particularly damaging effect on bone marrow. In fact, any rapidly dividing cells in the body are especially radiosensitive. This would include hair, skin, and the reproductive system. It is unfortunate that it took until the 1950s before X-ray fluoroscopes were removed from shoe stores. Parents were fascinated to see the bones of their child’s foot inside a new shoe without realizing that the radiation was harmful.

Until 1970, the outlook for a child who developed bone cancer was very poor. In spite of amputation of the affected limb, 80 percent of the young patients died within two years. In 1972, Norman Jaffe and Emil Frei in Boston made a major breakthrough in therapy by giving their patients large doses of a drug called methotrexate after limb surgery. It was a new approach in chemotherapy to stop the cancer from spreading even though no metastasis was visible yet. The experimental drug was so powerful that other antidote drugs were given to control side effects. The first trial with seventeen children was very successful, with all of them still surviving after twenty-one months.

However, an article written in 1994 by Tim Beardsley summarizing the status of cancer in the United States came to a rather pessimistic conclusion. The cancer rate was higher and the likelihood of cure had not improved for most types of adult cancer since the “war on cancer” was initiated by President Richard M. Nixon in 1971. The cumulative effects of smoking, poor diet, and continuing exposure to harmful chemicals may help to explain this lack of progress. The good news was that the death rate from childhood cancer fell by almost half in that period. Early diagnosis and improved therapy have helped greatly. The family of a child with cancer can now look forward with substantial hope for a cure without recurrence.

Bibliography:

American Cancer Society (ACS). "What Are the Key Statistics about Bone Cancer?"American Cancer Society, Jan. 22, 2013.

Cady, Blake, ed. Cancer Manual. 7th ed. Boston: American Cancer Society, 1986.

Dollinger, Malin, et al. Everyone’s Guide to Cancer Therapy. 5th ed. Kansas City, Mo.: Andrews, 2008.

Dorfman, Howard D. and Bogdan Czerniak. Bone Tumors. St. Louis, Mo.: Mosby, 1998.

Eyre, Harmon J., Dianne Partie Lange, and Lois B. Morris. Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment, and Recovery. 2d ed. Atlanta: American Cancer Society, 2002.

Janes-Hodder, Honna, and Nancy Keene. Childhood Cancer: A Parent’s Guide to Solid Tumor Cancers. 2d ed. Cambridge, Mass.: O’Reilly, 2002.

MedlinePlus. "Bone Cancer." MedlinePlus, Apr. 10, 2013.